Automatically adjusting irrigation controller with temperature and rainfall sensor

ABSTRACT

Methods and devices are provided to automatically determine plant water requirements and adjust irrigation in order to make efficient use of water. In one implementation, an irrigation control unit comprises at least one input adapted to be coupled to and receive signals from a rainfall sensor and a temperature sensor, the signals corresponding to current values of an amount of rainfall and temperature. The unit also includes a memory storing historical values of a plurality of variables and a processor coupled to the at least one input and the memory. The processor is adapted to determine plant water requirements at least in part using the historical values of the plurality of variables and the current values of the temperature and the amount of rainfall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to irrigation and, in particular, to asystem and method for automatically controlling irrigation.

2. Discussion of the Related Art

It is becoming increasingly important that irrigation controllers makeefficient use of water. There have been several attempts to adjust theamount of water applied to landscape plant life based on weatherconditions. Some attempts are based on mathematical models (known asevapotranspiration or ET) to determine plant watering requirements basedon weather conditions. Most industry accepted ET models (such as thePenman-Monteith model) require weather data for temperature, solarradiation, humidity and wind speed. However, the sensors necessary toprovide this weather data can be expensive, and as in the case ofresidential controllers, often cost prohibitive. Attempts have been madeto create solutions that approximate the results of the ET models bystoring historical ET values which are adjusted using currently sensedtemperature. However, the results are often questionable since weatheris not always repeatable from year to year and factors other thantemperature affect ET. Others have tried alternatives to the accepted ETmodels in an attempt to approximate the accepted ET models. Theseapproaches again have unproven and uncertain results.

SUMMARY OF THE INVENTION

Several embodiments of the present invention generally relates to anautomatically adjusting controller that determines plant waterrequirements and adjusts irrigation in order to make efficient use ofwater.

One embodiment can be characterized as an irrigation control unitcomprising at least one input adapted to be coupled to and receivesignals from a rainfall sensor and a temperature sensor, the signalscorresponding to current values of an amount of rainfall andtemperature. The unit also includes a memory storing historical valuesof a plurality of variables and a processor coupled to the at least oneinput and the memory. The processor is adapted to determine plant waterrequirements at least in part by determining an evapotranspiration (ET)value based at least in part on the historical values of the pluralityof variables and the current values of the temperature and making anadjustment according to the current value of the amount of rainfall.

In another embodiment, the invention may be characterized as a methodfor use in irrigation control, and means for performing the method, themethod comprising the steps: receiving current values of an amount ofrainfall and a temperature from a rainfall sensor and a temperaturesensor, the current values corresponding to a geographic location;receiving stored historical values of a plurality of variables from amemory, the stored historical values corresponding to the geographicregion; determining an evapotranspiration (ET) value based on thehistorical values of the plurality of variables and the current value ofthe temperature; and determining plant water requirements based at leastin part on the ET value and the current value for the amount ofrainfall.

In another embodiment, the invention may be characterized as a methodfor use in irrigation control comprising the steps: receiving, via auser interface of an irrigation control unit, user entered historicalvalues of one or more environmental variables useful in determiningplant water requirements, the user entered historical valuescorresponding to the geographic region; storing the user enteredhistorical values in a memory; receiving current values of one or moreother environmental variables useful in determining the plant waterrequirements from one or more sensors coupled to the irrigation controlunit, the current values corresponding to the geographic region, the oneor more other environment variables being different from the one or moreenvironmental variables; storing the current values in the memory;receiving one or more of the user entered historical values of the oneor more environmental variables from the memory; receiving one or moreof the current values of the one or more other environmental variablesfrom the memory; and determining the plant water requirements based atleast in part using the one or more of the user entered historicalvalues of the one or more environmental variables and the one or more ofthe current values of the one or more other environmental variables.

In another embodiment, the invention may be characterized as anirrigation control unit comprising: a user interface adapted to receiveinputs from a user; a memory adapted to store environmental variables;at least one input adapted to be coupled to and receive signals from oneor more sensors; and a processor coupled to the memory and the userinterface. The processor is adapted to: receive, via the user interface,user entered historical values of one or more environmental variablesuseful in determining plant water requirements, the user enteredhistorical values corresponding to the geographic region; store, in thememory, the user entered historical values received from the userinterface; receive, via the at least one input, current values of one ormore other environmental variables useful in determining the plant waterrequirements from the one or more sensors, the current valuescorresponding to the geographic region, the one or more otherenvironment variables being different from the one or more environmentalvariables; store, in the memory, the current values received from the atleast one input; and determine plant water requirements at least in partusing one or more of the user entered historical values of the one ormore environmental variables and one or more of the current values ofthe one or more other environmental variables.

In another embodiment, the invention may be characterized as a methodfor use in irrigation control comprising the steps: obtaining anirrigation control unit configured and manufactured to determine plantwater requirements based at least in part on values of a plurality ofenvironmental variables, the irrigation control unit configured andmanufactured to receive current values of a first set of one or more ofthe plurality of environmental variables, the current valuescorresponding to a geographic region; determining a historical value ofeach of a second set of one or more of the plurality of environmentalvariables, the historical values corresponding to the geographic region,wherein the first set of the one or more of the plurality ofenvironmental variables are different environmental variables that thesecond set of the one or more of the plurality of environmentalvariables; and entering, via a user interface of an irrigation controlunit, the historical values of each of the second set of the one or moreof the plurality of environmental variables to be stored in anirrigation control unit for later use together with the current valuesof the first set of the one or more of the plurality of environmentalvariables by the irrigation control unit in determining the plant waterrequirements.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following more particulardescription thereof, presented in conjunction with the followingdrawings, wherein:

FIG. 1 is a block diagram illustrating an irrigation control unit inaccordance with one embodiment;

FIG. 2 is a block diagram of one embodiment of the irrigation controlunit of FIG. 1;

FIG. 3 is block diagram of another embodiment of the irrigation controlunit of FIG. 1;

FIG. 4 is a flow chart illustrating a method of determining plant waterrequirements in accordance with several embodiments; and

FIG. 5 is a flow chart illustrating a method of determining plant waterrequirements using one or more user entered historical values of one ormore environmental variables together with one or more current values ofone or more other environmental variables from one or more sensors inaccordance with several embodiments.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings. Skilled artisans willappreciate that elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale. For example,the dimensions, sizing, and/or relative placement of some of theelements in the figures may be exaggerated relative to other elements tohelp to improve understanding of various embodiments of the presentinvention. Also, common but well-understood elements that are useful ornecessary in a commercially feasible embodiment are often not depictedin order to facilitate a less obstructed view of these variousembodiments of the present invention. It will also be understood thatthe terms and expressions used herein have the ordinary meaning as isusually accorded to such terms and expressions by those skilled in thecorresponding respective areas of inquiry and study except where otherspecific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION

The following description is not to be taken in a limiting sense, but ismade merely for the purpose of describing the general principles of theembodiments of the invention. The scope of the embodiments should bedetermined with reference to the claims. The present embodiments addressthe problems described in the background while also addressing otheradditional problems as will be seen from the following detaileddescription. It is noted that, as used in this specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. As used herein,“comprising,” “including,” “containing,” “characterized by,” andgrammatical equivalents thereof are inclusive or open-ended terms thatdo not exclude additional, unrecited elements or method steps.

Referring to FIG. 1, a block diagram is shown illustrating an irrigationcontrol unit 100 in accordance with one embodiment. The irrigationcontrol unit 100 includes a processor 102 coupled to a memory 104, atleast one input 106 and an output 108. In some embodiments, theprocessor 102 and the memory 104 may be referred to collectively as amicrocontroller. A rainfall sensor 110 and a temperature sensor 112 arecoupled to the at least one input 106 in order to provide signaling thatcorresponds to sensed or measured values of temperature and rainfall. Insome embodiments, the rainfall sensor 110 and the temperature sensor 112are integrated into a combination rainfall and temperature sensor 114.In some embodiments, the input 106 also provides a user interface toallow a user to interact with the irrigation control unit 100, e.g., toprogram, configure or adjust setup parameters, program schedules, etc.In some embodiments, the input 106 also functions as a power connectionthat provides operational power to one or both of the sensors 110 and112. Furthermore, in some embodiments, the input 106 may also functionas an output allowing for bi-directional communication between theprocessor 102 and the sensors 110 and 112. The output 108 may be anyoutput to cause or interrupt irrigation or may be a control output toprovide messages to cause or interrupt irrigation. It is noted that inaccordance with preferred embodiments, the rainfall sensor 110 is asensor that provides a measurement of the amount of rainfall, as opposedto a rain cutoff switch sensor which detects when rainfall exceeds apredefined level to activate a switch to interrupt irrigation. Therainfall sensor 110 of many embodiments may also be referred to as raingauge or rainfall accumulation sensor.

According to several embodiments, the irrigation control unit 100comprises a programmable irrigation controller that controls water flowto one or more irrigation stations, where each irrigation stationcomprises a water flow control device such as a valve or pump (forexample, see FIG. 2). In other embodiments, the irrigation control unit100 is a control device that is coupled to a programmable irrigationcontroller (for example, see FIG. 3). In many embodiments, theirrigation control unit 100 is adapted to automatically receive sensedtemperature and rainfall data, automatically determine if irrigationshould occur and if so, automatically generate and/or adjust orinterrupt watering schedules on a periodic basis.

According to several embodiments, the irrigation control unit 100 isadapted to make efficient use of water by determining or calculatingplant water requirements on a periodic basis for plant life to beirrigated. In some embodiments, the memory 104 stores historical valuesof one or more of the variables needed to calculate the plant waterrequirements. In several embodiments, for example, the memory 104 storeshistorical values for the environmental variables of solar radiation,wind speed, and humidity. In some embodiments, rather than storinghistorical values of the environmental variable of solar radiation,solar radiation is estimated using stored values of one or more ofextraterrestrial radiation (RA), location information (e.g., latitude),time of year (e.g., day of year) and currently sensed temperature. Infurther embodiments, extraterrestrial radiation is not pre-stored inmemory, but is calculated from other variables as described furtherbelow. As is generally known in the art, extraterrestrial radiation isvalue that is a function of the angle at which the sun strikes the earthat different times of the year at a specific geographic location orlatitude, extraterrestrial radiation is not a measurement of theintensity of sunlight. Thus, in these embodiments, the memory 104 storeshistorical values for wind speed and humidity, and optionallyextraterrestrial radiation. In any event, these historical values arepreferably values corresponding to the geographic location of theirrigation control unit 100 and/or an irrigation controller coupled tothe irrigation control unit 100. In some forms, multiple sets ofhistorical values are stored in the memory 104, each set of historicalvalues corresponding to a different geographic location. In oneembodiment, for example, the user inputs an indication of a specificgeographic location, for example, by inputting a zip code, a map code(e.g., a THOMAS GUIDE code), a latitude and/or a longitude, elevation,or other geographic or regional identifier. The processor 102 uses thisinput to select which set of stored historical values will be used indetermining plant water requirements. In some embodiments, thehistorical values are pre-stored during manufacture and/or prior to saleof the irrigation control unit. In other embodiments, the historicalvalues are entered by the user via the input 106, which is helpful incases where historical values are not known for a given region that theirrigation control unit will be operated.

In one embodiment, plant water requirements are based on mathematicalmodels of evapotranspiration (ET), such as the industry acceptedPenman-Monteith model. The Penman-Monteith equation can be found in CropEvapotranspiration: Guidelines for Computing Crop Water Requirementspublished by Food & Agriculture Organization of the United States (June2000) and also located at http://www.fao.org on the internet, forexample, see http://www.fao.org/docrep/X0490E/X0490E00.htm specificallyand such as described in U.S. Publication Nos. 2004/0039489 and2006/0161309 to Moore, all of which are hereby incorporated by referencein their entirety. It should be noted that as used herein, the termevapotranspiration at least refers to the actual evapotranspiration orthe potential evapotranspiration determined from any of themethodologies now known or may become known in the future. This modelutilizes weather data for temperature, solar radiation, humidity andwind speed to determine the amount of moisture lost by plant life due toevaporation and transpiration, i.e., ET, typically expressed in terms ofinches of water. Typical systems include rain gauge sensors that measurean amount of rainfall, which can be used to offset a calculated ETvalue. According to several embodiments, on a periodic basis (e.g.,every day), the irrigation control unit 100 uses stored (in the memory104) historical average values of solar radiation (or alternatively,stored or calculated values of extraterrestrial radiation), humidity andwind speed together with currently sensed or measured temperature (fromthe temperature sensor 112) to calculate a reference ET value, oftenreferred to as ETo. This reference ET value is then adjusted accordingto currently sensed rainfall measurements from the rainfall sensor 110in order to determine a net or adjusted ET (generically, the plant waterrequirements) indicating how much water the irrigation control unit 100should supply. In some embodiments, prior to adjusting for measuredrainfall, the reference ET value is multiplied by a landscapecoefficient to provide an ET value. Such landscape coefficients are wellknown values derived from the plant type, plant density and shade factorinformation that a user enters into the controller during setup.Accounting for landscape coefficients allows for some local adjustmentto be factored into the ET calculation. Given the determined plant waterrequirements, the irrigation control unit 100 automatically determineswhether or not irrigation should occur during the period of calculationof the plant water requirements. If it is determined that irrigationshould occur, the irrigation control unit 100 automatically generatesand implements a watering schedule or adjusts or interrupts an existingwatering schedule to provide the amount of water needed by the plantlife. As is recognized in the art, this watering approach is based onthe needs of the plant life (i.e., it is a weather-based control system)as opposed to a time-based control system in which a watering scheduleset by user (who is often an unsophisticated user, particularly withresidential irrigation controllers). It is understood that other modelsmay be used to determine plant water requirements, such as the Penmanequation, the Blaney-Criddle equation, the Makkink equation, theHargreaves equation or other equation that can calculate or approximatean ET value, such as described in U.S. Publication Nos. 2004/0039489 and2006/0161309 to Moore, and U.S. Pat. No. 6,314,340 to Mecham, all ofwhich are incorporated herein by reference. For the Hargreaves equation,see Hargreaves, George H., “Defining and Using ReferenceEvapotranspiration”, Journal of Irrigation and Drainage Engineering,vol. 120, No. 6, pp. 1132-1139, November/December 1994, and such asdescribed in U.S. Pat. No. 6,314,340 to Mecham, both of which areincorporated herein by reference. Furthermore, one or more of thesemodels include sub-models to calculate or approximate one or more of theweather-based or environmental variables used in the model. For example,as described more fully below, a sub-model may approximate solarradiation from extraterrestrial radiation, geographic location (such aslatitude), minimum and maximum temperature, time of year, etc. Thus, itis understood that in some embodiments, one or more of these sub-modelsare used at least in part to determine the plant water requirements.

In some embodiments, it can be difficult to obtain reliable values forsolar radiation which are needed for determining plant waterrequirements based on conventional methods calculating ET. Many weatherservices no longer provide values for solar radiation as a measure ofthe intensity of radiation occurring on a given day. Additionally,current solar radiation tends to fluctuate from historical values ofsolar radiation due to varying cloud cover. Thus, in accordance withsome embodiments, solar radiation is estimated from stored or calculatedvalues of extraterrestrial radiation together with knowledge of thelocation (latitude) of the irrigation control unit 100, the time of yearand the minimum and maximum temperatures (sensed by the temperaturesensor 112) for the period of calculation of the plant waterrequirements (for example, one day). The estimation of solar radiationfrom these values is generally known and published, for example, in “FAOIrrigation and Drainage Paper 56” published by the Food and AgricultureOrganization of the United Nations, 1998, ISBN 92-5-104219-5, which isincorporated herein by reference. This publication provides that tocalculate or estimate solar radiation (Rs) from extraterrestrialradiation (Ra), the minimum temperature (Tmin) and the maximumtemperature (Tmax), the following equation taken from page 60 of the FAOpublication is used, by the processor 102:Rs=0.175*SQRT(Tmax−Tmin)*Ra   Eq. (1)

-   -   (SQRT is the square root operation)

The Ra value may be calculated by the processor 102 or may be pre-storedin the memory 104, such as in a lookup table of Ra values given thelatitude and day of year. If the Ra is calculated by the processor 102,the following equation taken from page 46 of the FAO publication may beused:Ra=37.59*d _(r) *[v _(s)*sin(j)*sin(d)+cos(j)*cos(d)*sin(v _(s))]  Eq.(2)

-   -   Where:    -   v_(s)=arccos[−tan(j)*tan(d)]    -   d_(r)=1+0.033*cos(2p/365*J)    -   d=0.409*sin(2p/365*J−1.39)    -   j=latitude in radians    -   J=day of the year.

Latitude is retrieved from the memory 104. Latitude may be entered bythe user into the irrigation control unit and stored in the memory.Alternatively, latitude may be determined from other location orregional variable/s (e.g., zip code, map code) entered by the user andstored in the memory 104. For example, the processor may utilize alookup table to correspond the user input location variable to alatitude value. The day of year is automatically determined by theprocessor 102 since the irrigation control unit will have been initiallyprogrammed with the date and time.

It is recognized that by relying solely on pre-stored historical valuesof the variables (such as environmental variables) needed to determinethe plant water requirements (i.e., no current data is sensed orprovided), watering needs of plant life are often miscalculated sincehistorical values of these variables are often averaged and notnecessarily reflective of current weather conditions. On the other hand,it may be cost prohibitive to obtain current or sensed values of all ofthe variables needed to determine the plant water requirements. Someattempts have been made to approximate ET calculations using unprovenmodels and/or sensing current values of temperature as an approximationof a current calculation of ET. Such techniques have been shown to beinaccurate. Furthermore, some weather or environmental variables may berelatively more consistent with historical values, while others arerelatively less consistent with historical values. Further, the cost ofobtaining current or sensed data for some weather variables is costly,in particular for residential applications. In an attempt to utilizeindustry accepted and proven models for calculating plant waterrequirements while at the same time striking a balance between accuracyin determining plant water requirements and the cost of obtaining sensedor current values of variables, several embodiments utilize proven andaccepted models for determining plant water requirements using (1)stored historical values for those variables that are expensive orimpractical to sense current values therefor and (2) using currentlysensed and local values for other variables that it is inexpensive andpractical to sense current values therefor. In several embodiments, theinput 106 receives signals corresponding only to the current valuestemperature and current measured rainfall. Thus, in some embodiments,the irrigation control unit does not use any sensors for humidity, solarradiation or wind speed. Historical average values stored in the memory104 specific to the region or location of the irrigation control unitare used for all other variables needed to determine the plant waterrequirements.

Thus, in some embodiments, processor 102 receives the currenttemperature measured by the temperature sensor 112 and the currentamount of rain fall measured by the rainfall sensor 110, and alsoreceives historical values for one or more values stored in the memory104 needed for calculating plant water requirements. For example in oneembodiment, the processor 102 receives stored historical measurementsfor humidity, wind speed and solar radiation from the memory 104. Inembodiments that estimate solar radiation at least in part usingextraterrestrial radiation, the processor 102 receives stored historicalmeasurements for humidity, wind speed and extraterrestrial radiationfrom the memory 104. In one variation, extraterrestrial radiation is notstored in memory 104, but is estimated according to Eq. (2) above; thus,only historical values of humidity and wind speed are stored in thememory 104. In some embodiments, since current values for temperatureand rainfall are sensed, the memory 104 does not store any historicalvalues of temperature or rainfall that are used to automaticallydetermine plant water requirements. Additionally, the memory 104 doesnot store historical plant water requirements, such as historical ETvalues. This is because the control unit 100 automatically calculatesplant water requirements based on local conditions and allows localflexibility and/or adjustments in the determination of the plant waterrequirements. Using the above described particular combination ofcurrent and stored historical values, the plant water requirements aredetermined (e.g., calculated, estimated, etc.). In some embodiments,this provides an advantage in that watering schedules or adjustments towatering schedules are determined using the known and provenmathematical models but without requiring currently sensed values forall variables used in the calculation. Additionally, the devices used toprovide the current values are typically less costly than correspondingdevices needed for the variables that are stored. This combination ofsensor device/s and stored variables eliminates the need to purchase anexpensive full weather station capable of sensing current values or theneed to receive periodic broadcasts of current values of thesevariables, which often requires a recurring subscription (e.g., payingfor the paging of information to an irrigation controller). Thisparticular combination may (but not always) result in a less thancompletely accurate calculation of the plant water requirements, butnevertheless results in the conservation of water. Further, thiscombination allows for a cost effective weather based irrigation controldevice to be produced for more widespread use than a control device thatuses currently sensed values for all variables. As many governments haverecognized the importance of water conservation and the need forirrigation systems not to overwater, it is important to produceinexpensive consumer and residential irrigation control devices thatautomatically irrigate based on local weather conditions and the needsof the plant life to be irrigated.

Depending on the embodiment, the determined plant water requirements maybe used in a variety of ways. In some embodiments, the plant waterrequirement is used at least in part to automatically determine ifirrigation should occur during the period of calculation (e.g., thatparticular day). In one embodiment, the decision of whether or not toirrigate is based on the concept of managed allowable depletion, such asdescribed in more detail with reference to FIG. 4. Once it is determinedthat irrigation should occur or be allowed, in one embodiment, the plantwater requirement is used at least in part to automatically create awatering schedule for one or more irrigation stations controlling theflow of water to an area to be irrigated. Typically, each irrigationstation includes a flow control device, such as a valve or pump, thatcontrols the flow of water therethrough to one or more sprinkler orwatering devices. The watering schedule may be as simple as defining astart time for irrigation and a duration for irrigation for eachstation. The duration may be implemented over one or more cycles. Inmany embodiments, the plant water requirements will determine ifirrigation is needed at a particular point in time, and if needed, thenfor how long irrigation is needed. Plant water requirements can berecalculated on a periodic basis as needed, for example hourly, daily,weekly, monthly, etc.

In another embodiment, the plant water requirement is again used atleast in part to automatically determine if irrigation should occurduring the period of calculation (e.g., that particular day). Then, theplant water requirement is used to adjust, modify or limit an existingwatering schedule. For example, for each station, an existing wateringschedule may be programmed to irrigate on defined watering days, atdefined start times, and for defined durations. If the calculated plantwater requirement indicates that watering is not needed on a particularwatering day, the already programmed irrigation schedule will beinterrupted on that day. If the calculated plant water requirementindicates that watering is needed on a particular watering day but formore or less than the predefined duration, the already programmedirrigation schedule will be adjusted or interrupted. For example,interruption of a programmed irrigation schedule can occur within theprocessor 102 (e.g., in the event the processor 102 is part of anirrigation controller) or can occur as a result of an interruption ofthe common line 222 return in a typical irrigation actuation line (e.g.,in the event the processor 102 is part of a control device coupled to anirrigation controller). Several embodiments of the invention are usedwith time-based preprogrammed irrigation schedules, while severalembodiments are used with weather-based and/or ET-based irrigationschedules.

Generally, while referring to historical and current values of variablesused to determine plant water requirements, historical values refer tovalues corresponding to previous periods of time in terms of weatherconditions whereas current values refer to values corresponding to acurrent period of time in terms of weather conditions. Depending on theembodiment and variability of weather conditions, historical values maybe considered a value as early as one date prior to the current time.

The historical measurements may be stored according to day of the year,month of the year, season of the year, particular time of a particularday of the year, or other periodic reference point. For example, in someembodiments historical data is stored for each day of the year for avariety of locations, such as in each zip code in the United States.

The at least one input 106 is adapted to receive signals from therainfall sensor 110 and the temperature sensor 112. In some embodiments,the rainfall sensor 110 and the temperature sensor 112 are integratedinto a combination rainfall and temperature sensor 114. In severalembodiments, the rainfall sensor 110 outputs a signal corresponding tothe amount of current rain fall. Additionally, one or more of therainfall sensor 110 and the temperature sensor 112 may be integratedinto or internal to the irrigation control unit 100. In someembodiments, one or more of the rainfall sensor 110 and the temperaturesensor 112 are external to the irrigation control unit 100 in a locationproximate to or local in relation to the location of the irrigationcontrol unit 100. In some embodiments, one or more of the sensors 110and 112 may be located away from or remote in relationship to thelocation of the irrigation control unit 100. According to differentembodiments, the at least one input 106 comprises one or more of awireline input, a fiber-optic input or a wireless input in order toreceive signals from sensors via wireline, fiber-optic connection, orwirelessly (e.g., using radio frequency or infrared signaling). In oneform, the processor 102 receives the signals from the at least one input106 and determines the number and type of sensor/s coupled to orintegral with the irrigation control unit 100. In some embodiments, theconnection between the at least one input 106 and the sensor 110 and 112is a two wire connection providing AC power from the irrigation controlunit 100 to the sensors 110/112. Thus, the at least one input 106 is apower and data interface. Bi-directional communication occurs over thetwo wires. For example, similar to multi-wire decoder based controlsystems, the irrigation control unit selectively power clips an AC sinewaveform provided to the sensors 110/112 to communicate data to thesensors 110/112. To communicate data back to the irrigation controlunit, the sensors 110/112 selectively short circuits the two-wire pathto draw current during a portion of the waveform that is designated forfeedback. This results in a voltage drop or a current draw which issensed by the irrigation control unit. The shorting or non-shorting ofthe two-wire path during the designated portion is sensed by the input106 and interpreted as logic 1 and 0, resulting in the communication ofdata from the sensors 110/112 to the irrigation control unit over thetwo wire interface. The two wire interface is designed without polarityso that the wires may be interchangeably connected and power and datacan be delivered.

Additionally, in one embodiment, the input 106 is adapted to receiveuser input values that are used as the historical values stored in thememory 104 for future use or to receive user input values that arecurrent values. User input current values may be used where the userdetermines or knows the current value of a variable and a sensor is notavailable. For example, the user input includes one or more of a keypad,a touchpad, a touch screen, a mouse, a dial, a switch, a button, a leveror other types of devices used to input information into the irrigationcontrol unit.

Generally, the memory 104 is any type of storage medium capable oftemporarily or permanently storing or buffering information, forexample, a built-in hard disk drive, non-volatile flash memory, RAM,ROM, EEPROM, removable/insertable memory or any combination thereof. Allor a portion of the memory 104 may be in the form of one or moreremovable blocks, modules or chips. The memory 104 need not be onephysical memory device, but can include one or more separate memorydevices. Furthermore, the memory 104 may be separate from or integratedwith the processor 102. The functionality of the processor 102 and thememory 104 may be implemented as one of more of hardware, software orfirmware.

The output 108 may be an output interface to cause irrigation, e.g., aninterface for one or more actuation lines to couple to flow controldevices (such as valves or pumps). In such case, the output 108 includescontrollable switches and drivers to switch AC voltage signals or DCpulse voltage signals to a particular actuation line. DC pulse signalsare commonly used with latching solenoids. In other embodiments, theoutput 108 is an encoder adapted to be coupled to a multi-wire pathcoupled to multiple decoder devices. In such case, the output 108switches and modulates an AC or DC signal with data instructing one ormore of the decoder devices to start or stop irrigation. In otherembodiments, the output 108 is a control message output that outputssignaling to a wireline or wireless transmitter to send control signalsto another device, e.g., an irrigation controller executing a wateringschedule. In further embodiments, the output 108 is a controllableswitch, e.g., that can electrically complete or break a return commonline path for irrigation actuation lines of another irrigationcontroller.

Referring next to FIG. 2, a block diagram is shown of one embodiment ofthe irrigation control unit of FIG. 1. In this embodiment, an irrigationcontrol unit 200 includes the processor 102, the memory 104 (which inthis embodiment, are collectively as a microcontroller 202), a userinterface 206 including a display 208 and user inputs 210, a sensorinput interface 212 and an output interface 214, all generally containedwithin or integrated with a housing 204. Also illustrated rainfallsensor 110 and the temperature sensor 112, one or more actuation lines218 each coupled to a flow control device 220 (e.g., a valve or pump)and a common line 222.

In this embodiment, the irrigation control unit 200 comprises aprogrammable irrigation controller including functionality in accordancewith several embodiments for automatically determining plant waterrequirements and creating, adjusting or limiting watering schedulesbased on a combination of current and stored historical weather andenvironmental data. That is, in one embodiment, a user interacts withthe user interface 206 to configure the irrigation control unit to allowit to automatically determine plant water requirements and generatewatering schedules to be executed by the processor 102. In otherembodiments, the user inputs, programs or creates one or more wateringschedules or programs stored in the memory 104 and executed by theprocessor 102. In a typical irrigation controller, the processor 102outputs signaling to the output interface 214 to cause actuation signals(e.g., AC voltage signals or DC pulse signals) to be applied to one ormore of the actuation lines 218. When an actuation signal is applied toa given actuation line 218, the corresponding flow control device 220 isactuated (e.g., opened or closed) to allow or stop watering. Forexample, the output interface 214 includes drivers and switches thatselectively switch a 24 volt AC power signal to one or more of theactuation lines 218. Additionally, the sensor input interface 212provides a coupling point for one or more sensors 216, such as thesensors described above. Signaling received at the sensor inputinterface 212 is sent to the microcontroller 202 for storage andprocessing. In other embodiments, the output interface 214 may be anencoder output to a multi-wire path (e.g., a two-wire path) includingmultiple decoder devices.

The user interface 206 includes user inputs 210 and the display 208. Theuser inputs include, for example, one or more of a keypad, a touchpad, atouch screen, a mouse, a dial, a switch, a button, a lever or othertypes of devices used to input information into the irrigation controlunit 200. The display 208 includes one or more of a display screen,indicator lights (e.g., LEDs), and audible indicators or other types ofdisplay devices. The user interface 206 is used to program and operatethe irrigation control unit 200. According to some embodiments, duringthe initial setup or at a later time, the user inputs a variety ofinformation, including, for example, location of the irrigation controlunit 200, day of the year, soil type, gradient of the landscape,vegetation or plant type that is to be watered, start times, wateringdurations, water windows, non-watering days, or other factors orvariables used in creating or adjusting watering schedules. In someforms, the location of the irrigation control unit 200 location isentered by inputting a zip code, a map code (e.g., a THOMAS GUIDE code)or elevation, longitudinal and/or latitudinal coordinate for thelocation to be irrigated. In several embodiments, the processor 102 usesthis location information to select a given set of historical valuesstored in the memory 104. Using the date and/or time, the processor 102determines what portion of the given set of historical values will beused in determining plant water requirements.

In some embodiments, the user interface 206 is used to enter historicaldata values for one or more of the variables used to determine the waterplant requirements. This historical data may be used to replace orsupplement any historical data already stored in the memory. In someembodiments where historical data is unknown for the region of operationduring manufacture, the user interface allows the user to enterhistorical data specific to the region of operation. In someembodiments, no historical data values are pre-stored prior to salebecause it is known beforehand that the irrigation control unit will besold for use in a region with unknown historical data.

In several embodiments, the sensor input 212 receives signals from therainfall sensor 110 and the temperature sensor 112 and forwards thisinformation to the processor 102 and/or the memory 104. These signalscorrespond to current values for the amount of rainfall and temperatureat the specific location of the irrigation control unit and/or theirrigation controller used to determine plant water requirements. In oneor more embodiments, the signals received at the sensor input 212 areelectrical signals representing the current temperature and the currentamount of rainfall. For example, a signal having a certain voltage levelcorresponds to a given temperature or amount of rain fall. Additionallyor alternatively, in some embodiments, the presence of a signal at thesensor input 212 corresponds to a given value. For example, the signalmay be a pulse signal, each pulse corresponding to a certain incrementalvalue of a variable. In other embodiments, the signals received at thesensor input 212 are data signals defining one or more valuescorresponding to the current temperature and/or current amount of rainfall. In each case, the signals received at the sensor input 212correspond to a current value of a given variable.

The sensor input 212 is adapted to receive signals in a variety of ways,e.g., by wireline, fiber optic cable, and wireless communication. Insome embodiments, the sensor input 212 is a power and data interface,delivering power (e.g., AC or DC power) to the sensors 110 and 112 andallowing bi-directional communications in a similar fashion as decoderbased irrigation control systems as described above. One or both of therainfall sensor 110 and the temperature sensor 112 are local sensors inthat they are located at or proximate to the location to be watered.Alternatively, one or both of the sensors 110 and 112 are remote sensorsin that they are located at a distance from the location to be watered.In some embodiments, the current values are broadcast by wireline and/orwirelessly and received at the sensor input 212. In some embodiments(not illustrated), sensors 110 and 112 are integrated into the housing204 of the irrigation control unit 200. In an alternative embodiment,the current values are input by the user, for example, via the userinterface 206. For example, the user may simply enter the current valuefor one or more variables. That is, in the appropriate menu option, theuser enters the current values known to the user other than by using asensor coupled to the irrigation control unit 200.

The processor 102 and the memory 104 are similar to that described inFIG. 1. The processor is generally coupled through one or moreelectrical connections (e.g., via a bus structure) to the user interface206, the output interface 214 and the sensor input 212. The processor102 is programmed to periodically automatically determine or calculateplant water requirements based on a plurality of variables. In manyembodiments, the processor 102 receives current values for thetemperature and the amount of rainfall. In one embodiment, the processorreceives the temperature and rain measurements either directly from thesensor input 212 or from the memory 104. Further, the processor 102receives pre-stored historical values for other variables, such as solarradiation, humidity and wind speed from the memory 104. The currentvalues of the rainfall and temperature and the one or more historicalvalues are then used to automatically calculate the plant waterrequirements. In one embodiment, the processor 102 uses the currentvalue of temperature and historical values for the humidity, solarradiation and wind speed to calculate a reference ET value, ETo. Inother embodiments, the processor 102 uses the current value oftemperature and historical values for the humidity and wind speed alongwith stored values of extraterrestrial radiation to estimate solarradiation to calculate the ETo (for example, see Eq. (1) above). Inembodiments where extraterrestrial radiation is not stored in memory104, but is estimated (for example, see Eq. (2) above), only storedhistorical values for humidity and wind speed are used to calculate theETo. In some embodiments, the reference ET value is multiplied by alandscape coefficient, K_(L), to provide an adjusted ET value. Thelandscape coefficient is a well known value derived from the plant type,plant density and shade factor information that a user enters into thecontroller during setup. Next, the processor 102 uses the current valuefor the amount of rainfall to offset the adjusted ET value and thereforearrives at the plant water requirements. As a result, in someembodiments, the plant water requirements are determined at least usinga combination of current values for of rainfall and temperature andstored historical values for one or more other variables neededaccording to the particular model to calculate the plant waterrequirements. Using the plant water requirements, the processor 102automatically determines if watering should occur, and if so,automatically determines a watering schedule to provide the amount ofirrigation to meet the plant water requirements. Advantageously,watering schedules or adjustments to watering schedules are determinedusing known and proven mathematical models for plant water requirements,but without requiring currently sensed values for all variables used inthe calculation. In one embodiment, the plant water requirements arebased on mathematical models of ET. Most industry accepted models, suchas the Penman-Monteith model require values for temperature, solarradiation, humidity and wind speed. Additionally, the calculated valuesof ET are offset in some embodiments by measurements of rainfall orother local factors.

As described above, the plant water requirements are used in differentways by the processor 102 in different embodiments. For example, in oneimplementation, the irrigation control unit 200 is programmed with awatering schedule including, for example, watering days, start times,frequency of watering per watering day, and durations for one or moreflow control devices 220. However, it is understood that a wateringschedule may not require all of these variables to be programmed. Forexample, one or more of these variables may be set or not otherwiseprogrammable. In one embodiment, a user inputs a start time and awatering duration to define a watering schedule for each station. Thisschedule is stored in the memory 104 and executed by the processor 102.However, the sensor input 212 receives currently sensed values for oneor more variables. These variables are stored in the memory 104. On aperiodic basis, the processor 102 automatically determines the actualplant water requirements, determines if irrigation should occur or beallowed and automatically makes adjustments to or overrides theprogrammed watering schedules. For example, the processor 102 determinesthe plant water requirements using current values for temperature andrainfall and stored historical values for one or more other variables,such as humidity, wind speed and solar radiation (or extraterrestrialradiation) such as described above. If it is determined that the plantsto be watered require less water than would be provided by theprogrammed watering schedule, the processor 102 adjusts the wateringschedule. For example, the processor 102 shortens watering durations oreliminates one or more watering events altogether. This adjustment oroverriding can be performed in the execution of the schedule or may beperformed by simply disallowing or disabling the output interface 214from outputting control signals on the actuation lines 218. For example,the processor 102 may generate a signal that opens a switch that breaksthe common line 222 that acts as a return line for the actuation lines218. Once broken, the electrical path for the signaling on the actuationlines is interrupted and the watering schedule is overridden orinterrupted. If it is determined that the plants to be watered requiremore water than would be provided by the programmed watering schedule,the processor 102 adjusts the watering schedule. For example, theprocessor 102 extends watering durations or adds one or more wateringevents.

In other embodiments, the user does not program a watering schedule asis normally understood. Instead, the user simply programs the processor102 (via the user interface 206) to define certain watering days andstart times, without defining watering durations or frequency ofwatering per day. Similarly, the user may instead program wateringwindows, i.e., periods of time on watering days during which irrigationis allowed. On a periodic basis (e.g., every day, every other day, everyweek, etc.), the processor 102 automatically determines plant waterrequirements based on the current values of rainfall amount andtemperature and historical values of one or more other variables asdescribed above. In several embodiments, the plant water requirementsare expressed in terms of a unit of measurement water (e.g., inches ormillimeters) that is lost by plant life and should be replenishedthrough irrigation. Once the plant water requirements are determined,the processor 102 determines whether or not the plant life requireswatering at all. If it is determined that watering is required, theprocessor 102 then determines what duration of watering (over one ormore irrigation cycles) will provide the determined plant waterrequirement. For example, if the plant water requirements (e.g., acalculated ET value adjusted by any rainfall received since the lastcalculation) result in that 0.25 inches of water should be applied bythe irrigation control unit 200, then the processor 102 determines(given flow control device 220 flow rate, water pressure, etc.) theduration of irrigation. The processor 102 then outputs signaling to theoutput interface 214 at the start time to cause irrigation for thespecified duration. In this embodiment, the watering schedule isautomatically calculated based on the plant water requirements, asopposed to adjusting or limiting a programmed watering schedule. Ineither case, these embodiments allow for the efficient use of water.

Referring next to FIG. 3, a block diagram is shown of another embodimentof the irrigation control unit of FIG. 1. In this embodiment, anirrigation control unit 300 is separate from (non-integrated with) atraditional programmable irrigation controller 330. The irrigationcontrol unit 300 includes the processor 102, the memory 104 (which inthis embodiment, are collectively as a microcontroller 302), a userinterface 306 including a display 308 and user inputs 310, a sensorinput 312 and an output interface 314, all generally contained within orintegrated with a housing 304. The irrigation controller 330 includes amicrocontroller 332, a user interface 334, and an output interface 214all generally contained within or integrated with a housing 336. Alsoillustrated is the rainfall sensor 110 and temperature sensor 112coupled to the sensor input 312, one or more actuation lines 218 eachcoupling the output interface 214 to a flow control device 220 (e.g., avalve or pump) and a common line 222.

In this embodiment, the irrigation control unit 300 is an add-on oraccessory control device that is coupled to the traditional programmableirrigation controller 330. As is well known, the controller 330irrigates based on programmed time-based watering schedules. Forexample, a user interacts with the user interface 334 to set or programone or more watering schedules stored in and executed by themicrocontroller 332. In one example, for each flow control device 220(often referred to as a zone or station), the microcontroller 332 isprogrammed to water on certain days and at certain times and for certaindurations as set by the user. As described above, when the scheduleindicates that watering should occur for a given flow control device220, the output interface 214 switches an activation signal on a givenactuation line 218 to the given flow control device 220 causing water toflow therethrough to one or more sprinkler devices.

According to several embodiments, the irrigation control unit 300periodically and automatically adjusts, interrupts and/or overrideswatering schedules implemented in the irrigation controller 330.Depending on the embodiment, the irrigation control unit 300 canautomatically operate together with the irrigation controller 330 oroperate completely independent of the irrigation controller 330 withoutits knowledge. In the illustrated embodiment, the irrigation controlunit 300 is coupled to the irrigation controller 300 in that the commonline 222 serially connects through the output interface 314 back to theoutput interface 214. In other words, the output interface 314 is in anelectrical position on the common line 222 in between each flow controldevice 220 and the output interface 214. In other embodiments, theirrigation control unit 300 is directly coupled to the irrigationcontroller 330 at an input (not illustrated) of the irrigationcontroller 330. For example, the output interface 314 may be coupled bywireline or wirelessly to an interface (not shown) of the irrigationcontroller 330 which is coupled to the microcontroller 332. In theseembodiments, the irrigation control unit 300 can communicate directlywith the microcontroller 332. One advantage of the illustratedembodiment is that the irrigation control unit 300 can be coupled to anyconventional programmable irrigation controller 330 independent of thefunctionality and make/model of the irrigation controller 330.

The user interacts with the user interface 306 to program the irrigationcontrol unit 300. In preferred form, the irrigation control unit 300should be programmed with the same or similar watering schedules ascontained in irrigation controller 330. In one embodiment, the userinputs the same preprogrammed watering schedules that are stored in theirrigation controller 330 into the irrigation control unit 300. Inanother embodiment, the user inputs only the watering days and starttimes programmed into the irrigation controller 330. In furtherembodiments, the output interface 314 monitors the common line 222 overtime and learns watering schedules programmed in the irrigationcontroller 330. For example, the output interface 314 is able to detectwhen an activation signal is applied to one of the activation lines 218by sensing current flow on the common line 222. The user interface 306may vary depending on different embodiments of the irrigation controlunit 300. For example, the user interface 306 is similar to the userinterface 206; however, not all embodiments require all components ofthe user interface 306.

Similar to the embodiments described above, the irrigation control unit300 includes stored historical values of environmental variables in thememory 104 (e.g., either pre-stored during manufacture, prior to sale orentered by the user) used at least in part to determine plant waterrequirements. Additionally, the control unit 300 receives signals fromthe rainfall sensor 110 and the temperature sensor 112 at the sensorinput 312 that correspond to current values including the amount ofrainfall and temperature used at least in part to determine plant waterrequirements. Periodically, the processor 102 automatically determinesthe plant water requirements such as described above. In differentembodiments, the processor 102 uses the determined plant waterrequirements in different ways. For example in one embodiment, if theprocessor 102 determines that watering is not needed on a particularwatering day, then the processor 102 ensures that watering does notoccur on that day. For example, the processor 102 sends a signal to theoutput interface 314 to prevent irrigation. In one form, the outputinterface 314 comprises a controlled switch that when opened,electrically breaks the common line 222, which eliminates an electricalpath for any signaling on any of the actuation lines 218. In anotherform, the output interface 314 sends a signal to the microcontroller 332(via an input, not shown) instructing it to not irrigate on thatparticular day. In the event the microcontroller 302 determines thatwatering is needed but for a shorter duration than programmed, theprocessor 102 sends a signal to the output interface 314 at a specifiedtime after irrigation has begun but before irrigation should beconcluded. The output interface 314 then electrically breaks the commonline 222 to interrupt irrigation. Alternatively, the processor 102 sendsa signal to the microcontroller 332 via the output interface 314instructing it to irrigate for a shortened duration. In someembodiments, the programmed watering duration is set for the peakwatering duration that would be needed (e.g., set for peak summerwatering needs); thus, there is no need to irrigate for a longerduration than preprogrammed. These embodiments are preferred when theoutput interface 314 is coupled to and acts as a switch to interrupt thecommon line 222. In other embodiments, in the event the microcontroller302 determines that watering is needed during a particular period, butfor a longer duration than preprogrammed, the processor 102 sends asignal via the output interface 314 to the microcontroller 332 (directconnection not illustrated) to instruct it to temporarily increase theprogram duration.

Referring next to FIG. 4, a flow chart is shown that illustrates amethod of automatically determining plant water requirements inaccordance with several embodiments. These steps may be performed, forexample, by the irrigation control units described herein, such asirrigation control units 100, 200 and 300. Generally, in order to makeefficient use of water in an irrigation system in accordance withseveral embodiments, periodically, plant water requirements areautomatically determined based at least in part on a number ofweather-based or environmental variables which are used to create and/ormodify watering schedules. The plant water requirements are typicallybased on a mathematical model of the watering needs of plant life basedon a number of variables including one or more of, but not limited to,temperature, solar radiation, extraterrestrial radiation, humidity, windspeed, rainfall and soil moisture content. In preferred form, the plantwater requirements are based on models for the evapotranspiration (ET),such as provided by the Penman-Monteith model, as described above. Otherknown models or approximations may be used. Sensors are provided tooutput currently sensed values of rainfall and temperature used todetermine plant water requirements. Additionally, historical values forone to more of these variables are pre-stored into a memory ofirrigation control unit. The pre-stored values may be average or meanhistorical values for a given period of time, such as day, week, month,season, etc. In some embodiments, the pre-stored historical data valuesare stored in the irrigation control unit during manufacturing orotherwise prior to sale. In other embodiments, the pre-stored historicaldata is stored or loaded into the irrigation control unit atinstallation, for example downloaded or transferred from an externalmemory device into the memory of the irrigation control unit (e.g., viaa computer or other input connection of the user interface). In otherembodiments, the stored historical data is entered by the user, forexample via the user interface. Such embodiments would allow the user toenter historical data for locations for which historical data isunavailable during manufacture or installation. In some embodiments, thehistorical data is pre-stored during manufacture, but can be replaced orsupplemented with historical data entered by the user via the userinterface.

Furthermore, other variables or configuration data may have already beenentered by a user. The user inputs may pertain to location, time of theyear, soil type, gradient of the landscape, vegetation type, or otherfactors that may affect water schedules. In preferred form, the locationinformation includes a zip code, a map code, a longitudinal orlatitudinal coordinate, and/or elevation information, to define thelocation that is being watered. In some embodiments, the user inputs thetime of the year or some other periodic reference point so thecontroller can determine the current date (day, week, month), season ortime of year. Additionally, in some embodiments, one or more of wateringwindows, start days, start times, are entered by the user. In someembodiments, the plant water requirements discussed below are adjustedby one or more local factors, such as some of the user enteredvariables.

Initially, current values of the amount of rainfall and temperature arereceived (Step 402). For example, these values are received at theprocessor 102 directly from the input 106 (from the rainfall sensor 110and the temperature sensor 112) or from the memory 104 (in the event thecurrent value/s from the input 106 are buffered in or temporarily storedin memory 104). It is noted that in several embodiments, historicalvalues for one or more of temperature, rainfall and ET are not stored inthe memory. Next, historical values for a plurality of variables neededto determine plant water requirements are received (Step 404). Forexample, these values are received at the processor 102 from the memory104. For example, in several embodiments, the processor 102 retrieveshistorical values for one or more of humidity, solar radiation,extraterrestrial radiation and wind speed stored in memory 104 (e.g.,pre-stored during manufacture or prior to sale or entered by the user).In some embodiments, only historical values are stored for humidity andwind speed. In other embodiments, only historical values are stored forhumidity, wind speed and either solar radiation or extraterrestrialradiation are stored.

Next, plant water requirements are determined (e.g., calculated,estimated, etc.) at least in part using the current values of rainfalland temperature and the historical values for one or more othervariables (Step 406). For example, in one embodiment, the processor 102calculates the plant water requirements by first calculating a referenceET value (ETo) using the current value of temperature and the historicalvalues from the set of variables. In preferred form, the processorautomatically calculates ET according to the Penman-Montieth model usingcurrent values of temperature and historical values for wind speed,solar radiation and humidity. In other embodiments, the processorautomatically calculates ET according to the Penman-Montieth model usingcurrent values of temperature and historical values for wind speed,extraterrestrial radiation and humidity. In such embodiments, solarradiation is estimated using the historical extraterrestrial radiationstored in the memory and corresponding to the geographic location of theirrigation control unit and the minimum and maximum currently sensedtemperature for the period of time (such as for a given day) (forexample, see Eq. (1)). In other embodiments, extraterrestrial radiationis estimated or calculated for use in calculating the solar radiation(for example, see Eq. (2)). In some embodiments, the reference ET valueis multiplied by a landscape coefficient to provide an ET value. Next,in one embodiment, the landscape coefficient-adjusted ET value or thereference ET value is offset by the current amount of rain fall toarrive at the plant water requirements, e.g., an adjusted ET. As aresult, in some embodiments, the plant water requirements areautomatically determined at least using a combination of current valuesfor rain fall and temperature and stored historical values for one ormore other variables. In some embodiments, multiple sets of historicalvalues are stored in memory, each corresponding to a differentgeographic location or region (e.g., defined by zip code, map code,latitude and/or longitude, elevation or other geographic identifier).The historical values corresponding to the specific geographic regionare used to determine the plant water requirements. Furthermore, thehistorical values used (e.g., retrieved from memory) are stored valuesthat correspond to the current date, season or time of year. In oneexample, if the current date is February 1, then the historical valuesthat correspond to February 1 are used, e.g., either historical averagevalues from previous years on this date, during the week of February 1,during the month of February, etc.

As discussed above, a variety of models may be used to determine theplant water requirements. Additionally, other factors or adjustments notprestored in memory and not provided by sensors may be used at least inpart to determine the plant water requirements. For example, user inputvariables such as crop characteristics, soil characteristics, slope,etc. may be used depending on the particular model used by theirrigation control unit or any local adjustments made. In oneembodiment, plant water requirements are determined using thePenman-Monteith model that uses temperature, solar radiation, humidityand wind speed to calculate an adjusted ET value which is then adjustedby an amount of rainfall received since the last determination. In someembodiments, solar radiation is estimated using temperature andextraterrestrial radiation. Furthermore, in some embodiments,extraterrestrial radiation is estimated or calculated.

Several embodiments may be used with a variety of models or equations todetermine the plant water requirements. For example, several knownmodels used to calculate evapotranspiration (one example of plant waterrequirements) include the Penman equation, the Penman-Monteith equation,the Blaney-Criddle equation, the Makkink equation and the Hargreavesequation. Furthermore, one or more of these models include sub-models tocalculate or approximate one or more of the variables used in the model.For example, a sub-model may approximate solar radiation from minimumand maximum temperature, extraterrestrial radiation, location (such aslatitude), time of year, etc. Thus, it is understood that in someembodiments, one or more of the historical values are estimated orapproximated using one or more sub-modules and; therefore, one or moreof these sub-models are used at least in part to determine the plantwater requirements.

Next, it is determined if irrigation or watering should occur based atleast in part on the plant water requirements (Step 407). In someembodiments, irrigation should occur if the plant water requirementsexceed a specified threshold. In some embodiments, the decision ofwhether or not to irrigate is based on the concept of managed allowabledepletion. For example, That is, if the plant water requirements exceedan allowable water depletion level for the plant life to be irrigated,then it is determined that irrigation should occur. If the plant waterrequirements do not exceed the allowable water depletion level for theplant life to be irrigated, then the plant water requirements are savedand accumulated with the calculated plant water requirements for thenext calculation period (e.g., next day) and so on until the depletionlevel is exceeded. In other words, the plant water requirementsdetermined in Step 406 may be an accumulated plant water requirement,i.e., the calculated plant water requirements for the given period oftime (e.g., that day) plus the calculated plant water requirements froma previous period of time/s (e.g., previous day/s). Determining toirrigate based on managed allowable depletion is done in someembodiments in order to promote healthy plant growth. That is, the watercontent of plant life is allowed to deplete to a certain level beforereplenishing the depleted water content using irrigation in order topromote healthy growth.

Once it is determined that irrigation should occur (Step 407), the plantwater requirements are used differently in different embodiments.According to several embodiments, a watering schedule is automaticallycreated based at least in part on the plant water requirements (Step408). For example, if the plant water requirements are determined to be0.5 inches of water that should be applied to the plant life, then theduration of watering needed to supply 0.5 inches of water is determined.Then, at a given start time, watering is initiated for the calculatedduration. It is understood that the duration may be continuous or may bebroken up into separate periods of time or cycles (i.e., separate starttimes). The time between separate start times or cycles may be short orlong depending on the needs of the system, and may account for the slopeof the soil. If it is determined that irrigation is not needed (e.g.,the plant water requirements are negative), then watering is notsupplied.

In a typical implementation, a user has preprogrammed a start time andwatering days or otherwise programmed a watering window. Periodically(e.g., once per day), the irrigation control unit automaticallydetermines the plant water requirements and, for each watering day,determines if irrigation should occur. If irrigation should occur, theduration is calculated and watering is executed at the given start timefor the duration.

Once the watering schedule is created, the schedule is either executedor transmitted to the device that executes the watering schedule. Forexample, at the determined start time, signals are generated by aprocessor to cause an activation signal to be applied to a givenactuation line that will open/close a water flow control device (e.g., alatching or non-latching solenoid controlled valve or pump). Theactivation signal may be an AC voltage signal or DC pulse signal, forexample. In some cases, the voltage signal is modulated by an encoderthat outputs a signal to a multi-wire path having a plurality of decoderdevices coupled thereto. Each decoder device is typically coupled to oneor more water flow control devices.

According to several other embodiments, once the plant waterrequirements are determined (Step 406) and it is determined whether ornot irrigation should occur (Step 407), a programmed watering scheduleis adjusted based at least in part on the plant water requirements (Step410). In these embodiments, a preprogrammed water schedule exists, forexample, preprogrammed by a user into an irrigation control unit thatdetermined the plant water requirements (see for example, FIG. 2) orpreprogrammed into an irrigation controller coupled to an irrigationcontrol unit determining the plant water requirements (see for example,FIG. 3). In some embodiments, when it is determined that irrigationshould not occur, the schedule is completely interrupted or not allowedto irrigate. If it is determined that irrigation should occur, awatering duration is determined which when executed with provide thecalculated plant water requirements (which may be an accumulated amountof multiple periods of calculation). The schedule is then adjusted byinterrupting or overriding the scheduled watering at the appropriatetime to provide the proper duration of irrigation. Alternatively, acontrol message is generated to shorten the preprogrammed wateringduration. This occurs when the plant water requirements are less thanwould be provided by the watering schedule. In other embodiments, theschedule is adjusted when it is determined that more watering shouldoccur than preprogrammed, for example, by extending the wateringduration or adding additional watering events.

Once the watering schedule is adjusted, the adjusted schedule is eitherexecuted or transmitted to the device that executes the wateringschedule such as described above. Alternatively, the schedule beingexecuted by another irrigation controller is interrupted at theappropriate time to effect the adjustment. For example, referring to theirrigation control unit 300 of FIG. 3, the processor 102 determines whenwatering should be interrupted (or even allowed at all), and outputs asignal to the output interface 314 to open or electrically break thecommon line 222, stopping all irrigation at the flow control devices220. Alternatively, a signal is transmitted to the irrigation controller330 executing the water schedule to be adjusted, the signal instructingthat the controller should adjust the programmed water schedule.

Referring next to FIG. 5, a flow chart illustrates a method ofdetermining plant water requirements using one or more user enteredhistorical values of one or more environmental variables together withone or more current values of one or more other environmental variablesfrom one or more sensors in accordance with several embodiments. Forexample, in some embodiments, for some geographic regions where anirrigation control unit may be operated, historical data forenvironmental variables used to determine plant water requirements isunknown. In other embodiments, the stored historical data forenvironmental variables specific to a particular geographic region maynot necessarily be accurate for the particular location to be irrigatedby the irrigation control unit. In such cases, and other cases, a user(e.g., an end user, a contractor or a programmer) is allowed to entervalues for one or more variables that are stored in the irrigationcontrol unit as historical values for the one or more environmentalvariables. In such embodiments, the user interface of the irrigationcontrol unit, e.g., user interfaces 206 and 306, allow the user to entersuch information. For example, the appropriate menu displays aregenerated based on user manipulation of one or more controls (such asrotary dials, buttons, etc.).

Accordingly, from the viewpoint of the irrigation control unit, userentered historical values for one or more environmental variablescorresponding to a geographic region are received via a user interfaceof an irrigation control unit (Step 502). The historical values may beany data as determined by the user, whether the user obtains the datafrom a service or estimates the values based on measurements orapproximations. In preferred embodiments, the one or more variables mayinclude any of the variables described throughout this specification asbeing useful at least in part in determining plant water requirements,such as one or more of solar radiation, wind speed, and humidity. Insome embodiments, since the irrigation control unit can sensetemperature, user entered values are only received for one or both ofhumidity and wind speed. In such embodiments, the value for theenvironmental variable for solar radiation is estimated using currentlysensed temperature together with pre-stored values of one or more ofextraterrestrial radiation (RA), location information (e.g., latitude),and time of year (e.g., day of year) as described herein. Additionally,multiple historical values may be entered by the user for each of theenvironmental variables. For example, the user may enter a historicalvalue for each of a period of time (e.g., a day, a week, a month, aseason, etc.) for a given environmental variable. In operation, theirrigation control unit will use the user entered historical value thatmost closely corresponds to the date of use. In some embodiments, theuser entered historical value/s are the primary source of values for theenvironmental variables, not a backup source. For example, the userentered historical values are not used as a backup in the event valuesfrom a remote or other source are not available. Advantageously, thisembodiment does not rely on remote sources of values for variables andthus, the control unit can be simple and made cost effectively.

Next, the user entered historical values are stored in memory (Step504), e.g., memory 104. The user entered values may be added to thememory in addition to other manufacturer pre-stored historical valuesthat are stored in memory prior to the irrigation control unit beingsold that correspond to other geographic regions. Alternatively, theuser entered values may replace a set of manufacturer pre-storedhistorical values for the geographic region of the irrigation controlunit. Thus, in some embodiments, the memory of the irrigation controlunit contains pre-stored historical values for one or more of theenvironmental variables that will be used by the irrigation controlunit. These pre-stored values are supplemented or replaced by the userentered values. In some cases, the memory contains pre-stored values forsome of the environmental variables but does not pre-store historicalvalues for others of the environmental variables. In some cases, thememory contains no pre-stored historical values for environmentalvariables. In other cases, the memory stores pre-stored (before the saleof the irrigation control unit) historical values of one or moreenvironmental variables for each of multiple other geographic regionsbut does not store pre-stored historical values of one or more of theenvironmental variables for the geographic region to be irrigated.

Next, current values of one or more other environmental variables arereceived from one or more sensors coupled to the irrigation controlunit, the current values corresponding to the geographic region (Step506). The one or more other environment variables are different from theone or more environmental variables for which user entered historicalvalues have been received. In preferred embodiments, the one or moreother variables may include any of the variables described throughoutthis specification as being useful at least in part in determining plantwater requirements. For example, in preferred embodiments, the one ormore other environmental variables include temperature and an amount ofrainfall. In this case, current values of a sensed temperature and asensed amount of rainfall are received via an input of the irrigationcontrol unit from a temperature sensor and a rainfall sensor orcombination temperature and rainfall sensor. In some embodiments, thecurrent value/s are the primary source of values for the one or moreother environmental variables, not a backup source. For example, thecurrent values are not used as a backup in the event current values froma remote or other source are not available.

Next, the current values are stored in memory (Step 508), e.g., memory104, in addition to the user entered historical values and/or any othervalues pre-stored in memory prior to the irrigation control unit beingsold.

Once the values are stored, in some embodiments, the irrigation controlunit will begin automatic operation where it will use weather orenvironmental based data to automatically determine if irrigation isneeded and if so, either generate an appropriate watering schedule ormodify an existing watering schedule. Thus, in operation, one or more ofthe historical values are received (or retrieved) from memory (Step510). For example, the irrigation control unit will only receive thehistorical value or values of the multiple stored values entered by theuser that most closely corresponds to the current date of operation. Forexample, in one embodiment, the irrigation control unit receives astored user entered historical value for each of humidity and wind speedthat most closely corresponds to the current date of operation. In someembodiments, additional manufacturer pre-stored historical values may beretrieved from memory. Again, in preferred embodiments, the stored userentered historical values are the primary source, not a backup source ofvalues for the one or more environmental variables.

Next, one or more of the current values of the one or more otherenvironmental variables are received (Step 512). For example, in oneembodiment, the current value for temperature and an amount of rainfallare received (or retrieved) from memory. For example, such values storedin memory are received from a temperature sensor 112 and a rainfallsensor 110 as described herein. In some embodiments, the values arereceived from a memory that is temporarily storing the current values asthey are received from the appropriate sensors. Such stored sensorvalues are considered current sensed values since they have beenobtained a local sensor. Again, in preferred embodiments, the storedcurrent values are the primary source, not a backup source of currentvalues for the one or more other environmental variables.

Next, plant water requirements are determined based at least in part onthe one or more of the user entered historical values and the one ormore of the current values of the one or more other environmentalvariables (Step 514), if current values are to be used. Thisdetermination may be made according to any of the methods describedherein. For example, in some embodiments, plant water requirements aredetermined at least in part by determining an evapotranspiration (ET)value based at least in part on the one or more of the user enteredhistorical values of the one or more environmental variables and thecurrent value of the temperature and making an adjustment according tothe current value of the rainfall. In one embodiment, the user enteredhistorical values for humidity and wind speed corresponding to thecurrent date are used with the current temperature and an estimation ofsolar radiation (based on the current temperature) to determine an ETvalue using known techniques, (such as the Penman-Monteith model), whichis then adjusted at least by the current value of the rainfall. Once theplant water requirements are determined, the irrigation control unit candetermine if watering is required and if so, create and implement awatering schedule or modify and run an existing watering schedule, suchas described herein. In some embodiments, the user entered historicalvalue/s and the current values are the primary sources of values for theenvironmental variables, not backup sources. For example, these valuesare not used as a backup in the event values from a remote or othersource are not available.

Generally, it is noted that the method of FIG. 5 may be implemented byone or more components of an irrigation control unit. For example, undercontrol and direction of a processor (e.g., processor 102), the methodof FIG. 5 is performed. Additional components are provided, such as auser interface, memory and sensor input. For a user's perspective, insome embodiments, the user obtains or is provided with an irrigationcontrol unit that is configured and manufactured to determine plantwater requirements based at least in part on values of a plurality ofenvironmental variables.

The irrigation control unit is also configured and manufactured toreceive current values of a first set of one or more of the plurality ofenvironmental variables, the current values corresponding to ageographic region. The user determines a historical value of each of asecond set of one or more of the plurality of environmental variables,the historical values corresponding to a geographic region, where thefirst set of the one or more of the plurality of environmental variablesare different environmental variables that the second set of the one ormore of the plurality of environmental variables. The user then enters,via a user interface of the irrigation control unit, the historicalvalues of each of the second set of the one or more of the plurality ofenvironmental variables to be stored in an irrigation control unit forlater use together with the current values of the first set of the oneor more of the plurality of environmental variables by the irrigationcontrol unit in determining the plant water requirements.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, other modifications,variations, and arrangements of the present invention may be made inaccordance with the above teachings other than as specifically describedto practice the invention within the spirit and scope defined by thefollowing claims.

1. An irrigation control unit comprising: at least one input adapted tobe coupled to and receive signals from a rainfall sensor and atemperature sensor, the signals corresponding to current values of anamount of rainfall and temperature; a memory storing historical valuesof a plurality of variables; and a processor coupled to the at least oneinput and the memory, the processor adapted to determine plant waterrequirements at least in part by determining an evapotranspiration (ET)value based at least in part on the historical values of the pluralityof variables and the current value of the temperature and making anadjustment according to the current value of the amount of rainfall. 2.The irrigation control unit of claim 1, wherein the plurality ofvariables comprises humidity and wind speed.
 3. The irrigation controlunit of claim 1, wherein the plurality of variables consists of humidityand wind speed.
 4. The irrigation control unit of claim 1, wherein theplurality of variables comprises extraterrestrial radiation, humidityand wind speed.
 5. The irrigation control unit of claim 1, wherein theplurality of variables consists of extraterrestrial radiation, humidityand wind speed.
 6. The irrigation control unit of claim 1 wherein theprocessor is adapted to estimate solar radiation based at least in parton a value of extraterrestrial radiation, the solar radiation used atleast in part to determine the ET value.
 7. The irrigation control unitof claim 1, wherein the historical values of the plurality of variablesare stored in the memory prior to the irrigation control unit beingsold.
 8. The irrigation control unit of claim 7, wherein the pluralityof variables does not comprise a temperature variable.
 9. The irrigationcontrol unit of claim 1, wherein the memory stores multiple sets of thehistorical values of the plurality of variables, each set of thehistorical values specific to a geographic region.
 10. The irrigationcontrol unit of claim 9, wherein based on a user input, the processor isadapted to select one of the multiple sets of the historical values foruse in determining the plant water requirements.
 11. The irrigationcontrol unit of claim 9, wherein the plurality of variables does notcomprise a temperature variable.
 12. The irrigation control unit ofclaim 1 further comprising at least one output adapted to be coupled toand control operation of irrigation flow control devices.
 13. Theirrigation control unit of claim 1 further comprising at least oneoutput adapted to be coupled to an irrigation controller coupled to andcontrolling operation of irrigation flow control devices.
 14. Theirrigation control unit of claim 1 further comprising: the rainfallsensor coupled to the at least one input; and the temperature sensorcoupled to the at least one input.
 15. The irrigation control unit ofclaim 14 wherein the rainfall sensor and the temperature sensor comprisea combination rainfall and temperature sensor.
 16. The irrigationcontrol unit of claim 1, wherein the processor is adapted to determine,based at least in part on the plant water requirements, whetherirrigation should occur.
 17. The irrigation control unit of claim 1,wherein the processor is adapted to determine, based at least in part onthe plant water requirements, a watering schedule in order to meet theplant water requirements.
 18. The irrigation control unit of claim 1,wherein the processor is adapted to determine, based at least in part onthe plant water requirements, an adjustment to a programmed wateringschedule.
 19. The irrigation control unit of claim 1, wherein thehistorical values of the plurality of variables are retrieved from thememory, the memory storing multiple values of the plurality ofvariables, wherein the multiple values comprise values representative ofa historical condition for each of a plurality of time periods of aprevious year.
 20. A method for use in irrigation control comprising:receiving current values of an amount of rainfall and a temperature froma rainfall sensor and a temperature sensor, the current valuescorresponding to a geographic location; receiving stored historicalvalues of a plurality of variables from a memory, the stored historicalvalues corresponding to the geographic region; determining anevapotranspiration (ET) value based on the historical values of theplurality of variables and the current value of the temperature; anddetermining plant water requirements based at least in part on the ETvalue and the current value for the amount of rainfall.
 21. The methodof claim 20, wherein the plurality of variables comprises humidity andwind speed.
 22. The method of claim 20, wherein the plurality ofvariables consist of humidity and wind speed.
 23. The method of claim20, wherein the plurality of variables comprises extraterrestrialradiation, humidity and wind speed.
 24. The method of claim 20, whereinthe plurality of variables consists of extraterrestrial radiation,humidity and wind speed.
 25. The method of claim 20 further comprising:estimating solar radiation based at least in part on a value ofextraterrestrial radiation, the solar radiation used at least in part inthe determining the ET value step.
 26. The method of claim 20 furthercomprising: receiving a user input indicating the geographic region froma plurality of geographic regions; and selecting the stored historicalvalues of the plurality of variables from multiple sets of thehistorical values of the plurality of variables stored in the memorybased on the user input, each set of the historical values specific to aparticular geographic region.
 27. The method of claim 20 furthercomprising determining, based at least in part on the plant waterrequirements, whether irrigation should occur.
 28. The method of claim20 further comprising determining, based at least in part on the plantwater requirements, a watering schedule in order to meet the plant waterrequirements.
 29. The method of claim 20 further comprising determining,based at least in part on the plant water requirements, an adjustment toa programmed watering schedule.
 30. The method of claim 20 wherein thereceiving the current values step comprises receiving the current valuesof the amount of rainfall and the temperature from a combinationrainfall and temperature sensor.